The police used tear gas against several thousand protesters in and around central Cairo's Tahrir Square, birthplace of the 18-day uprising that toppled authoritarian leader Hosni Mubarak in February. The protesters pelted the police with rocks.

The violence is stoking tensions just more than a week before the start of the country's first post-Mubarak parliamentary elections, and comes at a time when the nation is roiled by a political storm over plans put forward by the military-backed government to enshrine a political role for the military in the next constitution and shield it from any civilian oversight.

"We have a single demand: The marshal must step down and be replaced by a civilian council," said protester Ahmed Hani, referring Field Marshal Hussein Tantawi, Egypt's military ruler and Mubarak's longtime defence minister.

"The violence yesterday showed us that Mubarak is still in power," said Hani, who was wounded in the forehead by a rubber bullet. He spoke over chants of "freedom, freedom" by hundreds of protesters around him.

Rocks, shattered glass and trash covered most of Tahrir early Sunday. Several hundred protesters were camping out on the lawn of the square's traffic island. All roads leading to the square were blocked by protesters who ran ID checks on anyone coming into the plaza.

Sunday's clashes, which were mostly on a road leading from Tahrir to the Interior Ministry, appeared likely to grow.

Protesters were using social networking sites on the internet to call on Egyptians to join them, and there were reports of several demonstrations headed to the square, including one from Cairo University.

The military, which took over from Mubarak, has repeatedly pledged to hand over power to an elected government but it has yet to set a specific date. According to one timetable floated by the military, the handover will take place after presidential elections are held late next year or early in 2013. The protesters say this is too late and accuse the military of dragging its feet. They want a handover to take place immediately after the end of parliamentary elections in March.

On Saturday, police fired rubber bullets, tear gas and beat protesters with batons, clearing the square at one point and pushing the fighting into surrounding side streets of downtown Cairo.

A 23-year-old protester died from a gunshot, said Health Ministry official Mohammed el-Sherbeni. At least 676 people were injured, he said. One other protester also was killed in Alexandria, where clashes also took place, said a security official, speaking on condition of anonymity because he was not authorised to talk to journalists.

After nightfall, protesters swarmed back into Tahrir in the thousands, setting tires ablaze in the street and filling the area with an acrid, black smoke. Police appeared to retreat to surrounding areas, leaving protesters free to retake and barricade themselves inside the square. The air was thick with stinging tear gas.

The government urged protesters to clear the square.

A member of the military council, Maj. Gen. Mohsen el-Fangari, said protesters' calls for change ahead of the election were a threat to the state.

"What is the point of being in Tahrir?" he asked, speaking by phone to a private TV channel. "What is the point of this strike, of the million marches? Aren't there legal channels to pursue demands in a way that won't impact Egypt ... internationally?"

"The aim of what is going on is to shake the backbone of the state, which is the armed forces."

In a warning, he said, "If security is not applied, we will implement the rule of law. Anyone who does wrong will pay for it."

Saturday's confrontation was one of the few since the uprising to involve the police, which have largely stayed in the background while the military took charge of security. There was no military presence in and around the square on Saturday or on Sunday. The black-clad police were a hated symbol of Mubarak's regime.

Some of the wounded had blood streaming down their faces and many had to be carried out of the square by fellow protesters to waiting ambulances. Human rights activists accused police of using excessive force.